You cannot restore trust while signaling that no steps will be taken to prevent the further fall of the greenback. Capital, be it to shore up financial institutions, or buy up much-devalued U.S. assets -- in terms of some currencies, U.S. real estate has plunged by more than 40% -- will stay on the sidelines as long as the Federal Reserve and the government do not take action to fix monetary policy.

In a Financial Times op-ed the other day, Alan Greenspan says that a measure of stability will be restored when house prices stabilize, which may be accurate. But why would capital flow into real estate denominated in dollars that are still expected to plunge?

The view expressed on this page by former Federal Reserve Board member Robert McTeer -- that the Fed now must give priority to the liquidity crisis and neglect the dollar -- is inaccurate, too. The liquidity crisis and the stable dollar are related. The vast extension of credit since 2002 could have never happened if the Fed had sustained a stable value for the dollar. . . .

The issue isn't that "we will never have a perfect model of risk," as Mr. Greenspan appears to think. What we need is accountability, not perfection. With the proper anchor, central banks can sustain a stable value for their currency, and that is what they must be held accountable for. If they do that, even if financial institutions experiment with a wide range of innovations they cannot expand credit too much.

The weak-dollar crowd only thinks of tradeable goods on international markets, a market that plays out over months or years. They make no space in their models for constantly adjusting asset prices and the crucial real-time investment decisions that drive the economy. With a more stable dollar, for instance, Bear Stearns could easily have found the capital to cover its losses and sustain its operations. But weak-dollar uncertainty causes panic and chases investors away.